What Causes Swelling And Numbness In Leg?

Hi, I'm a 21 years old young athlete , its been 3 days now that I feel mi left leg swollen and a bit numb. Its stars on the knee all the way down to the feet. Its like a pressure, concentrated on the feet. It bothers me while walking and also can feel the pressure while resting the leg, what can cause a thing like this, what should i take care off or what specialist should i visit?